<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>这是一个标题</title>
</head>
<body>
    <h1>这是一级标签</h1>
    <h2>这是二级标签</h2>
    <h3>这是三级标签</h3>
    <h4>这是四级标签</h4>
    <h5>这是五级标签</h5>
    <h6>这是六级标签</h6>
</body>
</html>